Consider BMI in vit D repletion

Overweight and obese patients may require higher doses of vitamin D to achieve vitamin D repletion, Australian researchers report. In an overview published in the American Journal of Medicine, the doctors from St Vincent’s hospital and Concord hospital in Sydney said their results challenge existing recommendations that vitamin D supplementation be based on baseline serum 25-OH D concentrations alone. Their retrospective review of 95 patients attending a minimal trauma fracture clinic at Concord hospital found that BMI correlated negatively with serum 25-OH D concentrations and positively with serum intact parathyroid hormone (iPTH) (p=<0.01 for both). In a regression analysis to determine the effect of age, sex, BMI, serum calcium and iPTH concentrations only BMI and iPTH independently predicted lower 25-OH D levels. In a separate longitudinal study of 17 hospitalised patients with severe vitamin D deficiency a similar relationship was observed. The 25-OH D level achieved in this group following one week of vitamin D replacement was highly dependent on BMI, the study authors said. Further studies are required to clarify whether the larger dose requirement in obese individuals is due to substrate deficiency or sequestration or excessive consumption. “However, irrespective of the mechanism, BMI should be considered in vitamin D supplements because overweight and obese individuals might require a larger dose (or longer duration) of supplementation to achieve sufficient serum 25-OH D levels,” they concluded. Am J Med 2009; 122: 1060....